7.8 - Sankey Diagrams

Flow diagrams

A flow diagram shows which stores energy moves between and how each transfer happens.

• Boxes represent energy stores.
• Arrows represent energy transfers.
• Labels on arrows state the transfer mechanism (e.g. mechanically, electrically, by heating, or by radiation).

Example - A ball thrown straight up

As a ball rises and slows, with air resistance acting on it:

• Energy leaves the ball's kinetic energy store and is transferred mechanically (work done against the gravitational force) to its gravitational potential energy store.
• At the same time, energy is transferred mechanically (work done against air resistance) to the internal energy stores of the ball and the surrounding air.

Unlike a Sankey diagram, a flow diagram does not have to show the amounts of energy - it shows the route between stores and the mechanism of each transfer.